Mechanical conical scanning techniques for antenna tracking systems have been in use for many years. A typical implementation for a mechanical conical scanning antenna system is where the antenna is of the Cassegrain type. In the Cassegrain configuration a subreflector is rotated at high speed so as to obtain a mechanical conical nutation within a certain angle of rotation which defines the scan region covered by the antenna beam. The conical scan can determine errors in the positioning of the antenna, since the amplitude of the received signal will be modulated by the mechanical nutation imparted by the rotating subreflector. When, through the nutative movement, an optimal position has been determined for the antenna, a separate device, typically an elevation over azimuth actuator is used to finally position the antenna structure. This is most commonly used in ground based applications since the inertial characteristics of ground based antenna do not warrant movement of the entire antenna structure in a nutative fashion to impart the conical scan. It is therefore necessary to provide separate electronic subsystems and separate physical rotative subsystems to impart the mechanical conical scan and tracking error detection in the systems that are known today.
Other scan techniques are the sequential lobing method or monopulse methods. In these systems the nutation is provided by a moving RF signal from the antenna feed. This also requires separate systems for error detection and correction. In both cases the actuator is typically of the elevation over azimuth type.
Therefore it would be greatly advantageous to integrate the actuating function which performs the error detection, and the actuating function which provides the signal error correction in a simple, single mechanism. Such an integrated system would find particular application in space based satellites where inertial characteristics are less critical than in ground based antennae.